That's an interesting idea, but I think it suffers from the same problem Wikipedia does - there's a large amount of noise, and a large amount of dubious information. In addition, while I don't know how often Google Maps updates their images, any new buildings are not represented.
To give a couple of examples, I live in an area of Syracuse colloquially known as "The Hill," where among other things is where Syracuse University is located. Right off the bat I noticed that the area east of campus was marked as "Off Campus Housing," which is completely disingenuous. Not only are there a good deal of families that live there (mostly older people), but it's hardly the only off-campus living area in the area. Similarly, I noticed a bunch of addresses where people marked in where they live... this falls under the category of trivial information, and under Wikipedia guidelines would be deleted. Finally, there are a couple of very important new buildings being built on SU campus - a third building for the very well known Newhouse school, and an additional five-story wing for the Life Sciences department. Neither can be found on Google Maps, and thus on Wikimapia, depspite being notable.